The present invention relates to a harvester in general, and more particularly to a drive arrangement for driving the cutting members of the harvester.
There are already known various types of cutting arrangements of the type here under consideration. The present invention will concentrate on a cutting arrangement for use in a harvester, but it will be appreciated that the concepts of the present invention can also be used to advantage in different types of cutting arrangements. When speaking of a harvester in the context of the present invention, it is to be understood that it includes, but it is not limited to, a mower, a hay harvester, a combined harvester-thresher and other devices for severing crops or plants from the stratum in which they grow.
Usually, the harvesters of this type include cutting elements at least one of which is movable relative to the other so that the stems or stalks of the plants which are to be severed which enter between the cutting edges of the cutting elements during the advancement of the harvester are severed by the combined action of the cutting edges of the cutting members. There are also already known such cutting arrangements in which both cutting members are driven into displacement relative to the frame of the harvester, which improves the cutting efficiency of the cutting arrangement. Usually, such cutting arrangements are driven into displacement by means of a motor, which may be the same as that advancing the harvester, or a separate motor, such as a hydraulic motor. The motor may drive a crank and the crank, in turn, may angularly displace levers which are pivoted to the frame and to the cutting members, via connecting rods. The present invention will be discussed as being embodied in a cutting arrangement in which both of the cutting members reciprocate along a common plane, and some of the conventional cutting arrangements of this type will now be discussed, together with their disadvantages.
In one cutting arrangement of this type, a hydraulic motor is supported on an inwardly located bracket, and an angularly displaceable link is interposed between the motor and a respective one of the cutting elements, which link has connecting portions spaced various distances from the axis of angular displacement of the link for connecting a respective connecting rod moved by the motor and the cutting element thereto. In this conventional arrangement, the hydraulic motor drives a doubly eccentric crank which is connected to the respective links which are mounted on the frame of the harvester for movement about a shared axis, via the connecting rods. In this arrangement, the connecting portions of the links are located at the elevation of the axis of rotation of the crank, and the above-mentioned axis is supported on additional brackets which are connected to the first-mentioned bracket.
This cutting arrangement is disadvantageous in that the links are mounted for angular displacement in vertical planes and conduct part-circular movements in the vertical planes as a result of the above-mentioned particular configuration of the drive arrangement. These vertical movements are transmitted to the rear parts of the cutting elements which, in turn, conduct part-circular movements in parallel horizontal planes due to the support of the cutting members on the frame of the harvester by means of horizontally angularly displaceable support arms. This combination of vertical and horizontal movements of various components of the cutting arrangement results in a situation where the rear portions of the cutting members are subjected to excessive and superfluous stresses which, in turn, may result in a rather rapid fatigue deterioration of the material of the cutting members and the disintegration of the latter. A further disadvantage of this conventional arrangement is to be seen in the fact that the cutting members will spread apart from one another when the cutting arrangement is operated at high speeds, in the vertical direction. When this happens, at least one of the cutting members will be spaced from the common plane at which the plants are to be severed, which will considerably impair the cutting efficiency of the cutting arrangement and, under some circumstances, it may result in clogging or jamming of the cutting arrangement. A still another drawback of this conventional arrangement is that the driving arrangement can only be located at one of the longitudinal ends of the cutting arrangement, inasmuch as at least one bracket is needed for the support of the links, which must be located frontwardly of the cutting members when considered in the direction of advancement of the harvester, and this bracket forms an obstruction in the way of faultless introduction of the stems of the plants toward and into the cutting arrangement. This latter drawback is particularly pronounced, and generates the most problems, when the cutting arrangement is to be located frontwardly of the harvester. More particularly, under such circumstances, it is necessary for proper weight distribution and suppression of oscillations to arrange the driving arrangement approximately in the middle of the harvester. Thus, this particular arrangement cannot be used in connection with a cutting arrangement which is to be located frontwardly of the harvester.
There is further known a driving arrangement for a laterally driven cutting arrangement with a pair of oppositely reciprocating cutting members, in which the upper and the lower driving links have different effective lengths. When speaking of an effective length throughout the specification, it is meant to designate the distance between the pivot points at the frame of the harvester and at the cutting members, respectively. In this particular arrangement, the lines of application of the driving forces which commence at the pivot points of the driving links are so selected that they pass through the centers of gravity of the cutting members, in order to reduce the bending stress of the particular cutting member. Such an arrangement is rather complex and expensive, and it must be adapted to each particular length of the cutting member.